One of systems regarded after the three generation wireless communication systems is an Orthogonal Frequency Division Multiplexing (OFDM) system, which is capable of avoiding an inter-symbol interference as much as possible by virtue of low complexity.
The OFDM system is configured to convert serially input data into N parallel data and transmit the N parallel data by loading on N orthogonal subcarriers. The subcarrier maintains orthogonality at the level of frequencies. An Orthogonal Frequency Division Multiple Access (OFDMA) denotes a multiple access technology that the multiple access is embodied by independently providing some of available subcarriers to each user in a system employing the OFDM modulation method.
A technology, which is the most widely used among technologies capable of increasing capacities in connection with the OFDM, is MIMO. The MIMO is a short term of Multi Input and Multi Output, and indicates an algorithm for improving data transmission and reception efficiency by adapting a multiple transmit antenna and a multiple receive antenna, breaking with an algorithm using one transmit antenna and one receive antenna. That is, the MIMO technology is to implement capacity increase and performance improvement by using multiple antennas at a transmitting end (transmitter) or a receiving end (receiver) in a wireless communication system. Here, MIMO is also referred to a multiple antenna (multi-antenna).
Summarizing the aforementioned, a multi-antenna technology adapts a technology of aggregating data segments received via various antennas, without being dependent on a single antenna route, in order to receive one entire message. The multi-antenna technology can improve data rate within a specific range or increase a system range for a specific data rate, accordingly, it is an attractive next generation mobile communication technology, which can be broadly used for mobile communication terminals, relays and the like, namely, expected to overcome throughput limit of mobile communications, which has reached the limitation due to data communication extension or the like.
3GPP and IEEE 802.11 are undergoing a standardization task for a terminal, which can support not only the MIMO system but also a carrier aggregation (CA), by which more data can be transmitted to a terminal (or User Equipment (UE)) using different types of carriers. This aims to supporting wider bandwidths up to 100 MHz compared to the conventional LTE rel(release)-8. Hereinafter, a terminal is referred to as UE.
In general, a UE architecture is defined by basically regarding an intra-band CA which transmits data by aggregating carriers using a contiguous spectrum is basically regarded. However, the UE architecture is defined such that data for one UE can be transmitted even using a non-contiguous spectrum to the extent permitted by UE complexity. However, a UE baseband supporting an intra-band or inter-band as well as the MIMO system has an extremely complex architecture, which causes a problem that the UE capabilities should be considered when desiring to categorize such UEs according to frequency bands.
Consequently, UEs supporting the intra-band CA and UEs supporting the inter-band CA have been separately produced for the intra-band and the inter-band, respectively, which causes inefficiency in terms of using UEs. Hence, a single UE baseband architecture for supporting not only the intra-band but also the inter-band CA is required.